In healthcare facilities, a syringe is conventionally used in a medication dispensing operation, such as a mixing operation to prepare an injection solution or a drip-feed solution. A plurality of medicinal agents contained in medicinal solution containers, such as vial containers, are suctioned by the syringe and then mixed in the syringe to dispense a pharmaceutical preparation. The dispensed pharmaceutical preparation is stored in a container such as an infusion bag.
The syringe includes a cylinder of tubular shape having a solution port on one end and an opening on the other end thereof, and a piston inserted into the cylinder through the opening. When the medicinal agent is suctioned by the syringe from the medicinal solution container, the piston is moved in a direction where the piston is pulled out from the cylinder. When the medicinal agent is injected into the container, for example, infusion bag, the piston is moved in a direction where the piston is pushed into the cylinder.
To suction the medicinal agent from the medicinal solution container into the syringe, it is necessary to continuously drive the piston in the pull-out direction against a negative pressure. To inject the medicinal agent from the syringe into the infusion bag, it is necessary to continuously drive the piston in the push-in direction against a positive pressure generated by, for example, a filter interposed in a passage therebetween. A reaction force generated when the piston is driven against the negative pressure or the positive pressure is significantly large, possibly as large as a few 10N. During the dispensing operation, an operator conventionally manipulates the piston of the syringe held with one hand, while holding the medicinal solution container with the other hand. Depending on the circumstances, the operator may have to suitably retain a positional relationship between the medicinal solution container and the syringe relative to each other. It is such an annoying work to manipulate the piston against such a large reaction force as a few 10N while holding the syringe at a certain angle with one hand.
The Patent Document 1 discloses a syringe drive device to help an operator to manipulate a syringe when a constant flow of medicinal agent is administered to human body.
Referring to FIG. 15, a syringe drive device 600 disclosed in the Patent Document 1 includes a cylinder holding section 603 which holds a cylinder 602 of a syringe 601, and a piston drive section (slider) 605 which axially drives a piston 604 relative to the cylinder 602 held by the cylinder holding section 603. When a feed screw thread 608 is driven by a motor (not illustrated in the drawings), a driven member 607 engaged with the feed screw thread 608 linearly moves. The piston drive section 605 is coupled with the driven member 607 by means of a coupling member 606 to thereby drive the piston 604 in a direction where the driven member 607 moves.
There are syringes having different storage capacity, for example, from 50 cc, 30 cc, to 20 cc. The syringes thus having different storage capacities are different from one another in shape, more specifically, length of cylinder, length of piston, and dimension from outer periphery of cylinder to solution port (height dimension of solution port). Some syringes having an equal storage capacity may have different shapes because they were manufactured by different manufacturers or manufactured according to different technical standards. When the operator uses the syringe drive device to suction or inject the medicinal solution while holding the syringe with one hand and the medicinal solution container with the other, it is important that various syringes having different shapes are usable and the operator can equally handle the syringe drive device even if the syringe having different shape is used. If there is variability when the syringes respectively having different storage capacities are loaded and used in the syringe drive device in where a tip of an injection needle attached to the syringe is situated, the workability is significantly deteriorated. The device disclosed in the Patent Document 1 was not particularly designed to address syringes formed in different shapes and equal usability in this case.